Breaker structures of radial tires

ABSTRACT

The disclosure relates to an invention in a pneumatic tire for a vehicle which tire has a radial carcass and a tread provided with a breaker structure. The breaker structure comprises a plurality of radially disposed strips formed of cords disposed at various angles relative to the midcircumferential plane of the tire. The breaker strips are arranged and folded relative to each other to produce such stiffness as to cause substantially absolute adherence of the tire to the travelling surface at low or high ground speeds.

United States Patent [56] References Cited UNITED STATES PATENTS2,996,097 8/1961 Lugli 152/361 3,002,546 10/1961 Limmer 152/361 PrimaryExaminerArthur L, La Point Assistant Examiner-Robert SaiferAttorney-Stevens, Davis, Miller & Mosher ABSTRACT: The disclosurerelates to an invention in a pneumatic tire for a vehicle which tire hasa radial carcass and a tread provided with a breaker structure. Thebreaker structure comprises a plurality of radially disposed stripsformed of cords disposed at various angles relative to themidcircumferential plane of the tire The breaker strips are arranged andfolded relative to each other to produce such stiffness as to causesubstantially absolute adherence of the tire to the travelling surfaceat low or high ground speeds.

BREAKER STRUCTURES OF RADIAL TIRES The present invention relates to theso-called radial tires," namely, to tires provided with a carcass formedby cords lying in radial planes or fonning small angles with saidplanes, and concerns in particular the breaker structures of radialtires intended to travel at high speed.

The background of the invention establishes that radial. tires can beprovided with an annular breaker structure, disposed between the carcassand the tread to stiffen the tread. This structure, which in the presentspecification will simply be called breaker," has an important effect onthe tire behavior, according to its structure and its geometricalarrangement (namely the angular relationships between the cordsconstituting it). It is also known that, in particular for tiresintended to run at high speed, it is preferable to provide a tread asflat as possible so as to provide a large surface in contact with theground and to ensure consequently a high adherence of the tire to thelatter.

This is generally obtained by using as a breaker a very rigid structure,for instance one constituted by strips of cord fabric of metallicmaterial, disposed at a very low angle with respect to the longitudinaldirection of the tire, in order to reduce displacements of the cordsexisting in the central portion of the structure itself, which causedeformation of the curved path in the zone of the tread. While such aconstruction may ensure in any condition of operation the desiredflattening degree on the tread profile in the central portion of thetread (which flattening degree is determined by the requirements of agood comfort and of steerability of the vehicle), nevertheless does notproduce an analogous effect in the tread lateral portions.

It was in fact noticed that, at high speed, the tread profile tends todeforrnate, curving in such a way as to show a concavity towards theground, due to the poor belting effect of the lateral edges of thebreaker, with a consequent reduction in the adherence to the ground, andtherefore in the road holding and steering safety.

The present invention aims at providing a pneumatic tire having verygood road holding and driving safety at high speed, together with a highsoftness and a quite good travelling comfort even at normal speed.

Briefly summarized the invention comprises a radial carcass and a treadand is provided with a breaker structure disposed between the carcassand the tread. The breaker structure comprising two strips of cordfabric of metallic material folded in such a way as to form twoskirtings, the folding lines of the two strips facing the two treadcomers and constituting the edges of the breaker, and the cords of onestrip being crossed with respect to those of the adjacent strip. Thetire is characterized in that in the breaker structure the two stripsare folded in such a way that the two skirtings have respectively awidth ranging between 75 and 95 percent and between and 35 percent ofthe width of the breaker, and in that an additional strip of cord fabricof metallic material is provided, which is superimposed relative to thefolded strips and is less than or equal to the distance between theskirtings of smaller width of said strips, the cords of the foldedstrips being symmetrically inclined with respect to the longitudinaldirection by an angle between 15 and 30, and the cords of the additionalstrip being inclined, with respect to said direction, by an anglebetween 10 and preferably of opposite sign with respect to the angle ofthe immediately underlying folded strip.

Preferably, the two folded strips of breaker structure according to thepresent invention are arranged in such a way that the skirting ofsmaller width of the innermost strip is directed towards the tireoutside, whereas the corresponding skirting of the other strip isdirected towards the inside.

The additional strip superimposed relative to the folded strips ispreferably of a width equal to 45 percent of the distance between theskirtings of smaller width of the folded strips.

The breaker structure according to the present invention proves to beparticularly advantageous. In fact, although in the folded strips thecords are inclined at a somewhat high angle, these strips provide astructure of the stiffness necessary to provide the absolute adherenceof the tire to the ground both at low and at high speed, by virtue ofthe presence of the skirtings of smaller width. These skirtings,although they are present only at the edges of the breaker structure,reinforce this structure in the zones where a stiffening is chieflyrequired, since their cords are arranged along a direction opposite tothat of the cords of the skirtings of greater width belonging to therespective strips. The central part of the breaker is instead madelighter, with an evident positive influence on the travelling comfort ofthe tire at low speed, by virtue of the arrangement of the cords and ofthe reduction in the number of the strips.

The provision of the narrow outermost additional strip arranged in thecentral portion of the breaker structure at a very small angle withrespect to the longitudinal direction, is on the other hand, sufficientto prevent the movement of the cords of the underlying strips in thisportion during the travel of the tire at high speed, avoiding thereforea deformation of the tread; moreover, owing to the limited width of thisstrip its presence does not originate a serious negative influence onthe softness of the whole structure.

The present invention will be more clearly understood from the followingdetailed description, made with reference to the accompanying drawingsgiven by way of nonlimiting example, in which:

FIG. 1, depicts diagrammatically in section, the tread portion of a tireaccording to the present invention; and

FIG. 2, shows in plan view the breaker structure of the tire illustratedin FIG. 1, in which some parts are broken away to show the path of thecords.

In FIG. I, the tire comprises a tread l and a carcass 2 formed by cordslying in radial planes. A breaker 3 is inserted between the tread andthe carcass. This breaker comprises a first strip 4 of metallicmaterial, folded along a folding line 6, said line being disposed at oneof the edges of the breaker defined by the plane indicated with lineA-A, in such a way as to form a skirting 8 having a width equal to about25 percent of the width of the whole breaker.

The breaker 3 comprises moreover a second strip 5 of metallic material,folded like strip 4 to form a skirting 9 equal to the skirting 8 alongthe folding line 7, which latter is disposed at the edge of the breakerdefined by the plane indicated with line 8-8.

The cords of the larger skirtings of the strips 4 and 5 are parallel toone another and are inclined at an angle of 25, equal and symmetricalwith respect to the longitudinal direction.

A strip 10 of metallic material is disposed above the strip 5 and isarranged at the central portion of the breaker and has a widthcorresponding to 45 percent of the distance comprised between the twoskirtings of smaller width of the underlying strips. The cords of theadditional strip are inclined, with respect to the longitudinaldirection, by an angle of 15, and said inclination has a sense oppositeto that of the cords of the underlying strip, so that the crossing anglebetween the cords of these strips is 40.

It should be understood that the present invention is not limited to theabove illustrated examples, but that it includes any other alternativeembodiments deriving from the aboveindicated inventive principle.

What is claimed is:

l. A pneumatic tire for vehicle wheels, comprising a radial carcass anda tread and having a breaker structure disposed between said carcass andsaid tread, said breaker structure comprising at least two strips ofcord fabric of metallic material folded in such a way as to form twoskirtings, the folding lines of said strips facing one of the treadcomers and constituting the edges of the breaker, and the cords of onestrip being crossed with respect to those of the adjacent strip,characterized in that in the breaker structure the two strips are foldedin such a way that said skirtings have respectively a width rangingbetween 75 and 95 percent and between and 35 percent of the width of thebreaker, and in that an additional strip of cord fabric of metallicmaterial is provided, which is superimposed to the folded strips and isof a width less than or equal to the distance between the skirtings ofsmaller width of said strips, the cords of the folded strips beingsymmetrically inclined, with respect to the longitudinal direction, byan angle between 15 and 30, and the cords of the additional strip beinginclined, with respect to said direction, by an angle between 10 andpreferably of opposite sign with respect to the angle of the immediatelyunderlying folded strip.

2. A pneumatic tire as in claim 1, characterized in that the foldedstrips are arranged in such a way that the skirting of smaller width ofthe innermost strip is directed towards the tire outside, and thecorresponding skirting of the other strip is directed towards the insid3. A pneumatic tire as in claim 1 characterized in that the additionalstrip is of a width substantially equal to 45 percent of the distancecomprised between the skirtings of smaller width of said folded strips.

4. A tire for vehicles including a radial carcass and tread, a breakerstructure disposed between the carcass and tread, said breaker structurecomprising a plurality of radially spaced strips formed of cordsangularly disposed relative to the midcircurnferential plane of thetire, lateral edge portions of said breaker strips being folded relativeto each other to produce stiffness in the tire to cause substantiallycomplete adherence of the tire to the travelling surface at variousground speeds, said lateral portions of said strips being folded to formskirtings, the folding lines of said strips facing one of the treadcorners and constituting the edges of the breaker, and the cords of onestrip being crossed with respect to those of the adjacent strip,characterized in that in the breaker structure the two strips are foldedin such a way that said skirtings have respectively a width rangingbetween 75 and percent and between 15 and 35 percent of the width of thebreaker, and in that an additional strip of cord fabric of metallicmaterial is provided, which is superimposed to the folded strips and isof a width not greater than the distance between the skirtings ofsmaller width of said strips, the cords of the folded strips beingsymmetrically inclined, with respect to the longitudinal direction, byan angle between 15 and 30, and the cords of the additional strip beinginclined, with respect to said direction, by an angle between 10 and 20,preferably of opposite sign with respect to the angle of the immediatelyunderlying folded strip.

S. A pneumatic tire as in claim 4, characterized in that the additionalstrip is of a width substantially equal to 45 percent of the distancecomprised between the skirtings of smaller width of said folded strips.

1. A pneumatic tire for vehicle wheels, comprising a radial carcass anda tread and having a breaker structure disposed between said carcass andsaid tread, said breaker structure comprising at least two strips ofcord fabric of metallic material folded in such a way as to form twoskirtings, the folding lines of said strips facing one of the treadcorners and constituting the edges of the breaker, and the cords of onestrip being crossed with respect to those of the adjacent strip,characterized in that in the breaker structure the two strips are foldedin such a way that said skirtings have respectively a width rangingbetween 75 and 95 percent and between 15 and 35 percent of the width ofthe breaker, and in that an additional strip of cord fabric of metallicmaterial is provided, which is superimposed to the folded strips and isof a width less than or equal to the distance between the skirtings ofsmaller width of said strips, the cords of the folded strips beingsymmetrically inclined, with respect to the longitudinal direction, byan angle between 15* and 30*, and the cords of the additional stripbeing inclined, with respect to said direction, by an angle between 10*and 20*, preferably of opposite sign with respect to the angle of theimmediately underlying folded strip.
 2. A pneumatic tire as in claim 1,characterized in that the folded strips are arranged in such a way thatthe skirting of smaller width of the innermost strip is directed towardsthe tire outside, and the corresponding skirting of the other strip isdirected towards the inside.
 3. A pneumatic tire as in claim 1characterized in that the additional strip is of a width substantiallyequal to 45 percent of the distance comprised between the skirtings ofsmaller width of said folded strips.
 4. A tire for vehicles including aradial carcass and tread, a breaker structure disposed between thecarcass and tread, said breaker structure comprising a plurality ofradially spaced strips formed of cords angularly disposed relative tothe midcircumferential plane of the tire, lateral edge portions of saidbreaker strips being folded relative to each other to produce stiffnessin the tire to cause substantially complete adherence of the tire to thetravelling surface at various ground speeds, said lateral portions ofsaid strips being folded to form skirtings, the folding lines of saidstrips facing one of the tread corners and constituting the edges of thebreaker, and the cords of one strip being crossed with respect to thoseof the adjacent strip, characterized in that in the breaker structurethe two strips are folded in such a way that said skirtings haverespectively a width ranging between 75 and 95 percent and between 15and 35 percent of the width of the breaker, and in that an additionalstrip of cord fabric of metallic material is provided, which issuperimposed to the folded strips and is of a width not greater than thedistance between the skirtings of smaller width of said strips, thecords of the folded strips being symmetrically inclined, with respect tothe longitudinal direction, by an angle between 15* and 30*, and thecords of the additional strip being inclined, with respect to saiddirection, by an angle between 10* and 20*, preferably of opposite signwith respect to the angle of the immediately underlying folded strip. 5.A pneumatic tire as in claim 4, characterized in that the additionalstrip is of a width substantially equal to 45 percent of the distancecomprised between the skirtings of smaller width of said folded strips.